MBNL1 and myotonic dystrophy type 1: Effects of MBNL protein loss in DM1 have been studied in detail in vivo in Mbnl knockout mice, which showed that Mbnl1 and Mbnl2 have distinct functions, predominantly in muscle and brain respectively, but also that the two isoforms can partially compensate for each other’s absence [3,4,21,22].